Final answer:
The proper adjective formed from the proper noun 'Hungary' is 'Hungarian'.
Step-by-step explanation:
An adjective that can be formed from the proper noun 'Hungary' is 'Hungarian'.
So the complete sentence would be: Authentic Hungarian goulash contains paprika (Hungary).
This adjective is formed by adding the suffix '-ian' to the proper noun 'Hungary', which is a common way to form adjectives from proper nouns.